So, when you print something, you have no control of how each pixel translate into dot at all? So how do you find the finite or the absolute minimun number of dot that will directly translate into pixel for specific printer to maintain the maximum detail? What exactly will you benefit if you print it yourself or use some other well known but more expensive lab when all you need is big print on standard paper?

The translation of pixels into dots of ink is specific to each printer model and is a closely guarded secret. Epson has done a lot of research and they think they have the best approach. Ditto for Canon, etc.

Unless you are developing algorithms to translate pixel colors into ink dot patterns, and most of us aren't doing that, you can just ignore the dpi.

To repeat: ignore the dpi. Pixels per inch (ppi) is all that we care about, and all that we have control over.